Subdivisions View parameter using Multires or Subsurf modifiers no longer increases object resolution
It looks like you may have enabled the 'Use Simplify' option found in the 'Scene' tab of the 'Properties' area:



This option works as a 'cap' on the number of subdivisions that objects in the scene can have if the simplify subdivision level is set lower than the subdivision level on your objects.

So a simplify subdivison level of '2' will mean that no subsurf modifiers will be able to subdivide objects higher than level 2. Setting it to zero would effectively turn all subdivisions off.

It can be useful when you have a very dense scene, with many subsurf modifiers and want to render it quickly as a test.